The invention relates in general to optical position indicators and in particular to optical position indicators capable of detecting displacements on the order of 10 to 100 microns.
MicroElectroMechanical Systems (MEMS) is a technology developed in the 1980""s. Various methods for determining very small changes in displacement in MEMS have been used. In one method, the device (for example, a slider/barrier) is viewed under a microscope. The microscope""s objective grid markings are calibrated or compared to non-movable features of the slider and when the slider is moved, the distance traveled is compared to the objective markings.
A second method is to mount the slider on a single axis translation stage and mark the position of the slider. The slider is moved and the amount of movement of the translation stage required to return the slider to its original position is the net movement.
A third method is to attach one plate of a capacitor to the slider and the second plate of the capacitor to a stationary base. By placing a voltage on the capacitor, the change in capacitance caused by the slider moving can be measured electrically and correlated to the amount of displacement.
While the first method (microscope) allows direct observance of the moving slider, it requires bulky equipment and an optical window into the MEMS device. The microscope is acceptable for laboratory use but undesirable for real world systems. The MEMS devices may be located inside of equipment (for example, torpedoes) and impossible to observe with a microscope. The same problems occur using the translation stage method. The third method, using an influence sensor (capacitance), allows for the remote reading of the position. However, the capacitor method requires additional structures that must be added to the device (capacitor plates), a voltage that must be applied to read the position and a readout device to convert the capacitance to a displacement. The capacitor method requires an external source of power and specialized test equipment.
The goal of Safe and Arm indicators (or any simple indicator) is to give a direct reading to an observer without the use of additional equipment.
In one aspect of the present invention an optical position indicator comprises a stationary base; a member having a longitudinal axis, the member being displaceable with respect to the stationary base along the longitudinal axis between a first position and a second position, the member including a reflective notch having two sides, the two sides defining respective planes that intersect the longitudinal axis at 45 degree angles; a light source; a first optical fiber mounted on the stationary base, the first optical fiber having a receiving end for receiving light from the light source and an illuminating end for illuminating the notch with a conical beam of light, the conical beam of light having a central axis and being completely intersected by one of the two sides of the notch, the central axis of the conical beam of light being perpendicular to the longitudinal axis of the member; a second optical fiber mounted on the stationary base, the second optical fiber having a receiving end for receiving light reflected from the notch when the member is in the first position, the receiving end of the second optical fiber being parallel to the illuminating end of the first optical fiber, the second optical fiber having an indicator end; a third optical fiber mounted on the stationary base, the third optical fiber having a receiving end for receiving light reflected from the notch when the member is in the second position, the receiving end of the third optical fiber being parallel to the illuminating end of the first optical fiber, the third optical fiber having an indicator end; and an indicator for receiving light from the indicator ends of the second and third optical fibers and for indicating a position of the member.
In another aspect of the present invention an optical position indicator comprises a stationary base; a member having a longitudinal axis, the member being displaceable with respect to the stationary base along the longitudinal axis between a first position and a second position, the member including first and second reflective notches, each reflective notch having two sides, the two sides defining respective planes that intersect the longitudinal axis at 45 degree angles; a light source; a fiber optic splitter having one end for receiving light from the light source and another end that splits into first and second optical fibers, the first optical fiber being mounted on the stationary base, the first optical fiber having a receiving end for receiving light from the fiber optic splitter and an illuminating end for illuminating the first notch with a conical beam of light, the conical beam of light having a central axis and being completely intersected by one of the two sides of the first notch, the central axis of the conical beam of light being perpendicular to the longitudinal axis of the member; a third optical fiber mounted on the stationary base, the third optical fiber having a receiving end for receiving light reflected from the first notch when the member is in the first position, the receiving end of the third optical fiber being parallel to the illuminating end of the first optical fiber, the third optical fiber having an indicator end; the second optical fiber being mounted on the stationary base, the second optical fiber having a receiving end for receiving light from the fiber optic splitter and an illuminating end for illuminating the second notch with a conical beam of light, the conical beam of light having a central axis and being completely intersected by one of the two sides of the second notch, the central axis of the conical beam of light being perpendicular to the longitudinal axis of the member; a fourth optical fiber mounted on the stationary base, the fourth optical fiber having a receiving end for receiving light reflected from the second notch when the member is in the second position, the receiving end of the fourth optical fiber being parallel to the illuminating end of the second optical fiber, the fourth optical fiber having an indicator end; and an indicator for receiving light from the indicator ends of the third and fourth optical fibers and for indicating a position of the member.
In yet another aspect of the present invention an optical position indicator comprises a stationary base; a member having a longitudinal axis, the member being displaceable with respect to the stationary base along the longitudinal axis between a first position and a second position, the member including first and second notches, each notch having two sides, the two sides defining respective planes that intersect the longitudinal axis at 45 degree angles, one of the two sides having a reflective surface and the other of the two sides including a curved reflective grating for splitting white light into a spectrum; a white light source; a fiber optic splitter having one end for receiving light from the white light source and another end that splits into first and second optical fibers; the first optical fiber being mounted on the stationary base, the first optical fiber having a receiving end for receiving light from the fiber optic splitter and an illuminating end for illuminating the side of the first notch having a curved reflective grating with a conical beam of white light, the conical beam of white light having a central axis and being completely intersected by the curved reflective grating of the first notch, the central axis of the conical beam of white light being perpendicular to the longitudinal axis of the member; a third optical fiber mounted on the stationary base, the third optical fiber having a receiving end for receiving a first color of light reflected from the first notch when the member is in the first position, the receiving end of the third optical fiber being parallel to the illuminating end of the first optical fiber, the third optical fiber having an indicator end; the second optical fiber being mounted on the stationary base, the second optical fiber having a receiving end for receiving white light from the fiber optic splitter and an illuminating end for illuminating the side of the second notch having a curved reflective grating with a conical beam of white light, the conical beam of white light having a central axis and being completely intersected by the curved reflective grating of the second notch, the central axis of the conical beam of white light being perpendicular to the longitudinal axis of the member; a fourth optical fiber mounted on the stationary base, the fourth optical fiber having a receiving end for receiving a second color of light reflected from the second notch when the member is in the second position, the receiving end of the fourth optical fiber being parallel to the illuminating end of the second optical fiber, the fourth optical fiber having an indicator end; and an indicator for receiving the first and second colors of light from the indicator ends of the third and fourth optical fibers, respectively, and for indicating a position of the member.
In still another aspect of the present invention an optical position indicator comprises a stationary base; a member having a longitudinal axis, the member being displaceable with respect to the stationary base along the longitudinal axis between a first position and a second position, the member including first and second notches, each notch having two sides, the two sides defining respective planes that intersect the longitudinal axis at 45 degree angles, one of the two sides having a reflective surface and the other of the two sides including a curved reflective grating for splitting white light into a spectrum, a white light source; a fiber optic splitter having one end for receiving light from the white light source and another end that splits into first and second optical fibers; the first optical fiber being mounted on the stationary base, the first optical fiber having a receiving end for receiving light from the fiber optic splitter and an illuminating end for illuminating the side of the first notch having a curved reflective grating with a conical beam of white light, the conical beam of white light having a central axis and being completely intersected by the curved reflective grating of the first notch, the central axis of the conical beam of white light being perpendicular to the longitudinal axis of the member, a third optical fiber mounted on the stationary base, the third optical fiber having a receiving end for receiving a first color of light reflected from the first notch when the member is in the first position, the receiving end of the third optical fiber being parallel to the illuminating end of the first optical fiber, the third optical fiber having an indicator end; the second optical fiber being mounted on the stationary base, the second optical fiber having a receiving end for receiving white light from the fiber optic splitter and an illuminating end for illuminating the side of the second notch having a curved reflective grating with a conical beam of white light, the conical beam of white light having a central axis and being completely intersected by the curved reflective grating of the second notch, the central axis of the conical beam of white light being perpendicular to the longitudinal axis of the member; a fourth optical fiber mounted on the stationary base, the fourth optical fiber having a receiving end for receiving a second color of light reflected from the second notch when the member is in the second position, the receiving end of the fourth optical fiber being parallel to the illuminating end of the second optical fiber, the fourth optical fiber having an indicator end; a second fiber optic splitter having one end for receiving the first and second colors of light from the indicator ends of the third and fourth optical fibers, respectively, and another end for outputting one of the first and second colors of light, and an indicator for receiving one of the first and second colors of light from the fiber optic splitter and for indicating a position of the member.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the following drawing.